There are several considerations in bipolar transistor design and fabrication. Most notably, capacitance, particularly between the base and emitter of the transistor, should be minimized in order to attain a high rate of transistor switching. Minimal capacitance should also exist between the base and collector for the same reason. Minimization of capacitance through minimizing base-emitter area has been the major focal point concerning the layout of the base and emitter. Generally, not much emphasis has been placed on the reduction of current crowding. Bipolar transistors in recent technology tend to show considerable current crowding owing to their small and ever decreasing geometries. Current crowding results in most bipolar action occurring on the periphery of the transistor and in fact the bipolar action may further be affected by the current path from the base contact to the specific emitter edge. Further, full benefit is not received from the conventional bipolar transistor due to the fact that the most of its elemental constituents (i.e. its base, emitter and collector) are not effectively used during operation as shall be explained below.
One commonly used bipolar fabrication structure is shown in FIG. 1, a drawing which illustrates the top view layout of base contact 2 with respect to emitter 4. Although minimization of base resistance (r.sub.b) was the primary motivation behind the creation of this layout, note that the location of two base contacts as shown in FIG. 1, allows use of both sides of the emitter, each labeled FF and RR respectively, during bipolar action. In contrast, in the case where a single base contact is paired with a single emitter, only one side of the emitter is active. Current crowding would render the other sides of the emitter inactive. FIG. 2 is a drawing of such a case with a partial circuit schematic superimposed over the top view layout of single base contact 2 paired with single emitter 4. The partial circuit schematic shown in FIG. 2 is the result of assigning to a semiconductor chip surface area, distributed resistances and distributed transistors along with associated transistor modeling parameters (i.e. r.sub.b and emitter resistance, r.sub.e). In FIG. 2, distributed bipolar transistors are labeled T1, T2, and T3 respectively. Each distributed transistor is assumed to have the same Beta (.beta.). Further, the modeled parameters such as base resistance and emitter resistance respectively, are assumed to be the same The r.sub.b and r.sub.e are indicated according to subscript for its associated distributed transistor. Resistive paths from base contact 2 to emitter 4 are represented by resistors labeled R. Although not all resistive paths are illustrated, of those which are illustrated, the relative resistance of that path increases with the number of resistors along that path. Base contact 2 is assumed to be equipotentialed in voltage. As is readily apparent from FIG. 2, distributed transistor T2 is in a greater active state than distributed transistors T1 and T3 due to the lesser voltage at the bases of distributed transistors T1 and T3 as compared with the voltage at the gate of distributed transistor T2. This lesser voltage results from the greater mount of resistance encountered along circuit paths to the base of distributed transistors T1 and T3 as compared with distributed transistor T2.
Conceivably, distributed transistors like T1, T2 and T3 can be modeled all along the periphery of emitter 4. FIG. 3 best illustrates this with a schematic drawing which models the distributed resistances and distributed transistors all along the periphery of the emitter. FIG. 3 additionally illustrates the relative location of emitter 4 to base contact 2 through the superposition of the layout over the schematic portion of FIG. 2. The modeled distributed transistor resistances such as r.sub.b and r.sub.e are lumped together with other resistances and all resistances are indicated by resistors R. FIG. 3 once again demonstrates that the farther away the distributed transistor is from base contact 2, the less turned on or less active the distributed transistor is. Accordingly, distributed transistor T3 is in the most active state as compared with the remaining distributed transistors since it is physically nearer base contact 2 than the remaining distributed transistors. Further, distributed transistors T5 through T8 near side RR, are likely barely in an active state such that they can be considered turned off due to current crowding, the effect of which has been illustrated via the resistance paths shown in foregoing examples. Thus, a substantial portion of the distributed transistor hardly participates during transistor operation. Therefore a need exists to improve the effectiveness and efficiency of a bipolar transistor.